In recent years, as personal computers have widely spread over, digital cameras capable of easily inputting picked-up images in the digital cameras to the personal computers have gained popularity. Further, it becomes general that a digital camera is installed into an information processing apparatus, such as, a mobile computer, a cellular phone and a PDA (Personal Digital Assistance). As the digital camera gains popularity, a smaller digital camera is demanded. When the size of a camera becomes small, vibration accidentally transmits to the image pickup optical system of the camera and image-shake occurs. Accordingly, various zoom lenses having anti-shake mechanism for performing the shake compensation have been proposed. For example, Japanese Patent Applications Open to Public Inspection Nos. H10-90601 and 2002-107625 disclose a zoom lens of five lens groups having positive power, negative power, positive power, negative power and positive power in the order from the object side, in which all lenses of the fourth lens group having negative power or a plurality of lenses in the fourth lens group is arranged to shift in the direction, which is substantially perpendicular to the optical axis of the lenses in order to conduct shake compensation.
However, the zoom lens for shake compensation disclosed in Japanese Patent Applications Open to Public Inspection Nos. H10-90601 and 2002-107625, includes a lens group which is designed to shift in the direction substantially perpendicular to the optical axis of the lens to conduct the shake compensation and which is configured to also move along the optical axis to vary its power. As a result, the structure of anti-shake mechanism becomes complex and a zoom lens barrel becomes large.